name: Mutation Testing

on:
  pull_request:
    branches: [main]
  workflow_dispatch:   # Allows manual trigger from GitHub UI

env:
  CARGO_TERM_COLOR: always
  # Skip live SSH network checks in tests
  ENTANGLE_SKIP_REMOTE_CHECK: "1"

jobs:
  mutants:
    name: cargo-mutants
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0 # Fetch all history so git diff works

      - name: Install Rust (stable)
        uses: dtolnay/rust-toolchain@stable

      # Download and install pre-compiled cargo-mutants binary (saves ~2 mins of compilation time)
      - name: Install cargo-mutants
        uses: taiki-e/install-action@v2
        with:
          tool: cargo-mutants

      # Several integration tests run git operations and require a configured git identity
      - name: Configure git identity
        run: |
          git config --global user.email "ci@example.com"
          git config --global user.name "CI"

      # Generate diff against the base branch and run mutants on modified lines only
      - name: Run cargo-mutants
        working-directory: entangle
        run: |
          git diff origin/${{ github.base_ref }}... > ../pr.diff
          cargo mutants --in-diff ../pr.diff